Distributor breaker plate assembly

ABSTRACT

A breaker plate assembly for an ignition distributor includes a base plate and a circuit breaker mounting plate. A link is pivotally connected to the base plate at one point on the link and is pivotally connected to the mounting plate at another point on the link. Pin and slot means associated with the base plate and mounting plate control movement of the mounting plate relative to the base plate. A set of circuit breaker contact points actuated by a cam follower is attached to the mounting plate. Because of the structure used, the cam follower moves concentrically with respect to a rotatable cam that actuates the cam follower. Concentric movement of the cam follower maintains the ignition dwell time substantially constant during advancement and retardation of the ignition timing.

United States Patent 1 Beard Oct. 30, 1973 DISTRIBUTOR BREAKER PLATEPrimary ExaminerLaurence M. Goodridge ASSEMBLY Attorney-Keith I...Zerschling et al. 75 Inventor: Garr E. Beard Livonia, Mich. I 1 y 57ABSTRACT [73] Asslgnee: ri Company Dearbom A breaker plate assembly foran ignition distributor MIC includes a base plate and a circuit breakermounting [22] Filed: July 21, 1971 plate. A link is pivotally connectedto the base plate at one point on the link and is pivotally connected tothe [21] Appl' l64731 mounting plate at another point on the link. Pinand slot means associated with the base plate and mount- 52 us. Cl200/31, 123/117 A, 123/1465 A s plate control movement of mounting Plate[51] Int. Cl. H0111 19/62 ative t0 the base p A set of i i reaker c n ac[58] Field of Search 123/117 A, 146.5 A; points actuated y a camfollower is attached to the 200/19, 31, 31 A, 31 DP mounting plate.Because of the structure used, the cam follower moves concentricallywith respect to a [5 6] References Cited rotatable cam that actuates thecam follower. Concen- UNITED STATES PATENTS tric movement of the camfollower maintains the ignition dwell time substantially constant duringadvancegzagfg 'g ment and retardation of the ignition timing.

: 8 Claims, 5 Drawing Figures BACKGROUND OF THE INVENTION This inventionrelates to a breaker assembly for use in an ignition distributor for aspark ignition engine. More particularly, the invention concerns abreaker plate assembly having moveable means for advancing or retardingthe ignition timing during engine operation in response to changingoperating conditions. Typically, movement of the breaker plate assemblyin spark ignition eninges is obtained with a vacuum motor responsive toengine intake manifold vacuum.

. The usual ignition distributor for a spark ignition engine comprises adistributor housing having a rotatable shaft journaled therein. Theshaft at its upper portion has a cam attached to it for actuating a camfollower attached to the moveable arm of a circuit breaker that includesa pair of contact points, one of which is mounted on the moveablearm-Rotation of the arm alternately opens and closes the circuit breakercontact points. When the'points open, an electrical impulse results and,through theaction of the engine ignition coil, a spark is produced in acombustion chamber. The number of degrees of cam rotation during whichthe contact points remain closed is referred to as the dwell time and isof considerable importance. It is desirable for a number of reasons tomaintain this dwell time constant during the advancement and retardationof the ignition timing.

In order to obtain a constant dwell time, it is necessary that the camfollower attached to the moveable arm of the circuit breaker moveconcentrically with respect to the axis of the distributor cam duringthe advancement and retardation of the ignition timing.

Distributor breaker plate assemblies which will produce concentricmovement of the circuit breaker cam follower relative to the axis of therotatable cam are well known in the art. However, because of cost andreliability considerations, such prior art devices have been unsuitablefor general production usage. For this reason, the usual breaker plateassembly has comprised a circuit breaker mounting plate pivotallyconnected to a base plate fixed with respect to the distributor housing.The pivotal connectionubetween the two plates necessarily has been offthe axis of the rotatable distributor cam and movement of the mountingplate relative to the base plate about this pivotal connection toadvance or retard ignitiontiming has resulted in a change in dwell time.The novel breaker plate assembly of the invention may be madeinterchangeable with this usual prior art device, and it may bemanufactured at a comparable cost.

SUMMARY OF THE INVENTION In accordance with the invention, a breakerplate assembly for use in an ignition distributor having a housingadapted to receive a rotatable shaft and associated cam and having meansfor advancing or retarding the spark in response to engine operatingconditions comprises a base plate adapted for stationary mounting withrespect to the distributor housing. The base plate has a central openingtherein to permit the rotatable shaft to pass therethrough. A circuitbreaker mounting plate that may also have an opening therein to permitpassage of the rotatable shaft therethrough also is provided. A circuitbreaker is attached to the mounting plate. The circuit breaker has a setof contact points,

the set of contact points including a cam follower for opening andclosing the contact points in response to rotation of thecam. A link ispivotally connected at one point thereon to the base plate and atanother point thereon to the circuit breaker mounting plate. Guide pinand slot means associated with the base plate and with the mountingplate are provided for guiding the movements with respect to the baseplate of the mounting plate and the link about the pivotal connections.The guide pin is positioned within the slot. The guide pin may belocated in the base plate and the slot in the circuit breaker mountingplate, or, vice versa. A device, such as a hole or upstanding post, isprovided in the mounting plate for the attachment of the distributormeans for advancing or retarding the ignition spark in response toengine operating conditions.

Preferably, the mounting plate and link are positioned on opposite sidesof the base plate and resilient means are provided for urging themounting plate and link toward the base plate. Also, it is preferredthat the link be constructed from a plastic material and that it bepositioned within a recess in the base plate.

These and other constructional features of the breaker plate assembly ofthe invention are described in detail in the following specification andin the drawlngs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a distributorassembly incorporating a breaker plate assembly constructed inaccordance with the invention;

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1 andillustrates the breaker plate assembly with the circuit breaker contactpoints removed except for the cam follower;

FIG. 3 is a view taken along the line 3-3 of FIG. 2 and illustrates thebreaker plate assembly;

FIG. 4 is a view taken along the line 44 of FIG. 2 and illustrates thebreaker plate assembly with the circuit breaker mounting plate removed;and

FIG. 5 is a view taken along the line 5-5 in FIG. 2 and illustrates thelink used in the breaker plate, assembly.

DETAILED DESCRIPTION OF THE INVENTION With reference now particularly toFIGS. 1 and 2, a distributor shaft 12 is mounted rotatably within adistributor housing 14 by means of bearing 16. A cam 18 is carried bythe shaft 12 and is rotatable therewith. Rotation of the shaft 12is'obtained by the rotation of the gear 20 that meshes with another gear(not shown) driven by the engine.

Distributor means for advancing and retarding ignition timing inresponse to engine operating conditions is designated generally by thenumeral 22. This means may be a dual diaphragm vacuum motor of the typedescribed in US. Pat. Application Ser. No. 858,567, filed Sept. 11,1969, and assigned to the Ford Motor Company. The vacuum motor 22 has anactuating rod 24 that moves back and forth along the axial centerline 26of the vacuum motor in response to changing engine operating conditions.

The breaker plate assembly of the invention includes a base plate 28, acircuit breaker mounting plate 30, and a link 32. The link and both themounting plate and base plate have openings therein for the passage ofthe shaft 12 and associated cam 18 therethrough. The base plate 28 andmounting plate 30 preferably are made from metal stampings, and the'link32 preferably is made from a plastic material. Glass-filled nylon hasbeen found to be a suitable material for the link 32.

The base plate 28 of the breaker plate assembly is attached in a fixedor stationary manner to the distributor housing 14 along an annularledge or shoulder 34 with screws 36 (FIG. 1). The mounting plate 30 ofthe breaker plate assembly carries a circuit breaker 38 having a set ofcontacts 40. One of the circuit'breaker contacts is fixed with respectto the mounting plate, while the other contact is on a moveable arm 42which pivots about the point 44. The moveable pivot arm 42 has a camfollower 46 positioned in engagement with the rotatable cam 18. In aconventional manner, a capacitor 48 is connected throughits lead wire 50to a terminal 52 located on the circuit breaker 38. The terminal 52 isconnected electrically to the contact on the moveable arm 42. The fixedcontact is connected electrically through the lead wire 54 to thedistributor housing. A lead wire 56 also is attached to the terminal 52and has a connector 57 for attachment to an ignition coil (not shown).

Means for the attachment of the actuating rod 24 of the vacuum motor 22to the mounting plate 30 is provided by an upstanding post 58 affixed tothe mounting plate 30. This permits movements of the actuating rod 24 tobe transmitted to the mounting plate 30.

With particular reference now to FIG. 2, it may be seen that the link 32provides two pivot points for movement of the mounting plate 30 relativeto the stationary base plate 28. One of the pivot points is located at60 and pivotally connects the link 32 to the base plate 28. The pivotpoint 60 comprises a slotted boss 62 which is integral with the link 32.The slotted boss 62 mates with a flanged aperture 64 in the base plate28. The other pivot point 65 on the link 32 is formed by an integralpivot pin 66 that extends through an opening in the base plate 28 topermit the formation of a pivotal connection at 68 between the link 32and the mounting plate 30. Associated with and surrounding the pivot pin66 is a coil spring 70 which is held in position by a spring retainer72. The spring 70 urges both the link 32 and the mounting plate 30toward the base plate 28. Thus, it may be seen that base plate 28 isstationary with respect to'the distributorhousing 14, the link 32 ispivotally connected at 60 with the base plate 28, and the link 32 alsois pivotally connected by means of the pivot pin 66 with the mountingplate 30. Preferably, the pivot points 60 and 65 are locatedsubstantially opposite one another with respect to the openings in thelink, base plate, and mounting plate through which the rotatable shaft12 and cam 18 pass.

It is preferred that the link 32 be positioned within a recessed portion74 in the base plate 28. Also, it is preferable that the mounting plate30 be spaced from the base plate 28 to minimize contact therebetween.Three plastic buttons 76, one of which may be seen in section in FIG. 2and all of which may be seen in FIG. 3, are attached to the mountingplate 30 for this purpose. The plastic button which may be seen in FIG.2 is positioned within a recess in the mounting plate 30. The otherbuttons are not recessed.

With particular reference now to FIG. 3, there is shown a view of thefull breaker plate assembly with the capacitor and points removed. Thepositions of the cam 18 and cam follower 46 are shown with dot-dashlines.

It may be seen that the mounting plate 30 has an-opening 78 throughwhich the shaft 12 and its associated cam 18 may pass. Connected'withthe opening 78 is a rectangularly-shaped opening 80. Opening 80 permitsmovement of the mounting plate without interference with thelink-to-base plate pivotal connection formed by the slotted boss 62 andthe flanged aperture 64.

The mounting plate 30 has a slot 82 in which a guide pin 84 affixed tothe base plate 28 moves. Movement of the slot 82 along the guide pin 84provides control of the movements of both the mounting plate 30 and link32 relative to the stationary base plate 28, this movement occurringabout both of the pivot points 60 and 65. It is the pin and slot means82 and 84 which, through proper choice of slot shape and location, canbe made to provide concentric movement of the cam follower 46 relativeto the axis of the rotatable cam 18. As was previously stated, thismovement is provided by the vacuum motor actuator rod 24 attached to theupstanding post 58 on the mounting plate 30, the movement being impartedin response to changing engine operating conditions.

In practice, the guide pin 84 may be located in the mounting plate 30,rather than in the base plate 28. In such case, the guide slot 82 wouldbe located in the base plate 28. The location for the pin and slot meansassociated with the base plate and the mounting plate is not critical.However, the shape of the slot is dependent upon the location chosen forthe pin. Thus, a point may be chosen on the base plate for the locationof the pin and the mounting plate may then be moved about the pivotpoints 60 and 65 so that a desired path is taken by the cam follower 46.As this desired path is taken, a locus of points for the slot isdetermined. Generally, the locus of points will describe a curved pathfor the slot 82. However, when the slot is located approximately asshown in FIG. 3, the locus is very nearly a straight line. An elongatedand straight slot thus may be used.

Threaded holes 86 and 88 provide means for the attachment of the circuitbreaker contact point assembly 38 to the mounting plate 30. Threadedhole 90 provides a means for the attachment of the capacitor 48 to themounting plate 30. As is conventional, a locating boss 94 is provided toestablish the location of the capacitor 48. A cutout 92 in the mountingplate 30 permits it to move without interference with the screw 36 usedto attach the base plate 28 to the distributor housing 14.

With reference now to FIG. 4, it may be seen that the base plate 28 hasa central opening 96 through which the shaft 12 and associated cam 18may pass. A rectangularly-shaped opening 98 also is provided. Opening 98permits passage of the pivot pin 66 through the base plate 28 andpermits unrestricted movement of the pivot pin 66, this pivot pinproviding the pivotal connection between the link 32 and the mountingplate 30 as was previously described. The openings 96 and 98 are locatedin the recessed portion 74 of the base plate 28. In FIG. 4, thisrecessed portion 74 appears as a raised area. Apertures 100, 102, and104 in the base plate 28 are provided to permit unrestricted movement ofscrews or the like used to attach the capacitor and circuit breaker tothe mounting plate 30. A portion of the link 32, which is positionedwithin the recess 74 in the base plate 28, may be seen through theaperture 104.

The configuration of the link 32 may best be seen in FIG. 5. Link 32 hasa central opening 106 to permit passage therethrough of the shaft 12 andits associated cam 18. As was previously described, the pivot points 60and 65 are located at the slotted boss 62 and the pivot pin 66, thepivotal connections being located substantially opposite one anotherwith respect to the opening 106 in the link. Link 32 has raised bosses108, 110, 112, and 114. These bosses limit the amount of surface area oflink 32 that comes into actual contact with the base plate 28.Preferably, the bosses 112 and 114 are about one-half the height ofbosses 108 and 110. This permits the spring 70 surrounding the pivot pin66 to draw in the central portion of the link 32 and applies a biasforce to the pivotal connection 60.

Based upon the foregoing description of the invention, what is claimedand desired to be protected by Letters Patent is:

l. A breaker plate assembly for use in an ignition distributor for aspark ignition engine, said breaker plate assembly comprising: a baseplate, said base plate having an opening therein; a circuit breakermounting plate positioned on one side of said base plate; a linkpositioned on the other side of said base plate, said link beingpivotally connected at a first point thereon to said base plate, saidlink being pivotally connected at a second point thereon to saidmounting plate, said pivotal connection at said second point including apivot pin extending through said opening in said base plate, and saidlink having an opening therein, said first and second pivotal pointsbeing located at substantially opposite sides of said opening in saidlink; and guide pin and slot means associated with said mounting plateand with said base plate for guiding the movement of said mounting plateand link relative to said base plate about said first and second pivotalconnections; whereby, when said base plate is attached to saiddistributor and a force is applied to said mounting plate, said linkpivots about said first pivotal connection between it and said baseplate, said mounting plate pivots about said second pivotal connectionbetween it and.

said link, and said second pivotal connection moves relative to saidbaseplate, said movement of said second pivotal connection being guided bysaid guide pin and slot means associated with said mounting plate andbase plate.

2. A breaker plate assembly for use in an ignition distributor for aspark ignition engine, said distributor having a housing adapted toreceive a rotatable shaft and associated cam and having means foradvancing or retarding said spark in response to engine operatingconditions, said breaker plate assembly comprising: a base plate adaptedfor stationary mounting with respect to said housing of saiddistributor, said base plate having an opening therein to permit saidrotatable shaft to pass therethrough; a circuit breaker mounting platehaving an opening therein to permit passage of said rotatable shafttherethrough; a circuit breaker attached to said mounting plate, saidcircuit breaker having a set of contact points, said set of contactpoints including a cam follower for opening and closing said contactpoints in response to rotation of said cam; a link, said link beingpivotally connected to said base plate at a first point on said link andbeing pivotally connected to said mounting plate at a second point onsaid link, said pivotal connections being located substantially oppositeone another with respect to said opening in said base plate, guide pinand slot means associated with said base plate and with said mountingplate for guiding the movements relative to said base plate of saidmounting plate and said link about said pivotal connections; and meansin said mounting plate for the attachment of said distributor means foradvancing or retarding said spark in response to engine operatingconditions; whereby, when said base plate is attached to saiddistributor housing and a force is applied to said mounting plate bysaid means for advancing or retarding said spark, said link pivots aboutsaid pivotal connection between it and said base plate, said mountingplate pivots about said pivotal connection between it and said link, andsaid pivotal connection between said mounting plate and said link movesrelative to said base plate, this pivotal connection movement beingguided by said guide pin and slot means associated with said base plateand mounting plate.

3. A breaker plate assembly in accordance with claim 1, wherein saidmounting plate and said link are positioned on opposite sides of saidbase plate and wherein said guide pin and slot means comprises a slot insaid mounting plate and a pin affixed to said base plate, said pinextending into said slot for movement therein.

4. A breaker plate assembly in accordance with claim 1, wherein saidmounting plate and said link are positioned on opposite sides of saidbase plate and wherein said pivotal connection between said link andsaid mounting plate comprises a pivot pin integral with said link andextending therefrom through said opening in said base plate to permitpivotal connection with said mounting plate, and means in contact withsaid pivot pin for resiliently urging said mounting plate and said linktoward said base plate.

5. A breaker plate assembly for use in an ignition distributor for aspark ignition engine, said breaker plate assembly comprising: a baseplate, said base plate having an opening therein and said base platehaving a recessed portion; a circuit breaker mounting plate positionedon one side of said base plate; a link positioned within said recessedportion of said base plate and on the other side thereof, said linkbeing pivotally connected at a first point thereon to said base plate,and said link being pivotally connected at a second point thereon tosaid mounting plate; and guide pin and slot means associated with saidmounting plate and with said base plate for guiding movements of saidmounting plate and said link relative to said base plate; whereby, whensaid base plate'is attached to said distributor and a force is appliedto said mounting plate, said link piv ots about said pivotal connectionbetween it and said base plate, said mounting plate pivots about saidpivotal connection between it and said link, and said pivotal connectionbetween said mounting plate and said link moves relative to said baseplate, this pivotal connection movement being guided by said guide pinand slot means associated with said mounting plate and base plate.

6. A breaker plate assembly in accordance with claim 5, wherein saidpivotal connection of said link with said base plate at said first pointon said link comprises a slotted boss integral with said link and aflanged aperture in said base plate, said slotted boss being positionedwithin said flanged aperture.

7. A breaker plate assembly in accordance with claim 6, wherein saidpivotal connection of said link with said mounting plate at said secondpoint on said link comprises a pivot pin integral with said link andextending through said opening in said base plate to permit pivotalconnection with said mounting plate, and wherein said breaker plateassembly further comprises resilient means for urging said mountingplate and said link toward said base plate. a

8. A breaker plate assembly for use in an ignition distributor for aspark ignition engine, said breaker plate assembly comprising a baseplate, said base plate having an opening therein; a circuit breakermounting plate positioned on one side of said base plate; a linkpositioned on the other side of said base plate, said link beingpivotally connected at-a first point thereon to said base plate, saidlink being pivotally connected at a second point thereon to saidmounting plate, said pivotal connection at said second point including apivot pin extending through said opening in said base plate and saidpivotal connection at said second point having associated therewithresilient means for urging said mounting plate and said link toward saidbase plate; and guide pin and slot means associated with said base plateand with said mounting plate for guiding the movements relative to saidbase plate of said mounting plate and said link about said first andsecond pivot points, said slot of said guide pin and slot means beingelongated and substantially straight in shape, said guide pin of saidguide pin and slot means being movable in said slot; whereby, when saidbase plate is attached to said distributor and a force is applied tosaid mounting plate, said link pivots about said pivotal connection be-I tween it and said base plate, said mounting plate pivots and mountingplate.

1. A breaker plate assembly for use in an ignition distributor for a spark ignition engine, said breaker plate assemBly comprising: a base plate, said base plate having an opening therein; a circuit breaker mounting plate positioned on one side of said base plate; a link positioned on the other side of said base plate, said link being pivotally connected at a first point thereon to said base plate, said link being pivotally connected at a second point thereon to said mounting plate, said pivotal connection at said second point including a pivot pin extending through said opening in said base plate, and said link having an opening therein, said first and second pivotal points being located at substantially opposite sides of said opening in said link; and guide pin and slot means associated with said mounting plate and with said base plate for guiding the movement of said mounting plate and link relative to said base plate about said first and second pivotal connections; whereby, when said base plate is attached to said distributor and a force is applied to said mounting plate, said link pivots about said first pivotal connection between it and said base plate, said mounting plate pivots about said second pivotal connection between it and said link, and said second pivotal connection moves relative to said base plate, said movement of said second pivotal connection being guided by said guide pin and slot means associated with said mounting plate and base plate.
 2. A breaker plate assembly for use in an ignition distributor for a spark ignition engine, said distributor having a housing adapted to receive a rotatable shaft and associated cam and having means for advancing or retarding said spark in response to engine operating conditions, said breaker plate assembly comprising: a base plate adapted for stationary mounting with respect to said housing of said distributor, said base plate having an opening therein to permit said rotatable shaft to pass therethrough; a circuit breaker mounting plate having an opening therein to permit passage of said rotatable shaft therethrough; a circuit breaker attached to said mounting plate, said circuit breaker having a set of contact points, said set of contact points including a cam follower for opening and closing said contact points in response to rotation of said cam; a link, said link being pivotally connected to said base plate at a first point on said link and being pivotally connected to said mounting plate at a second point on said link, said pivotal connections being located substantially opposite one another with respect to said opening in said base plate, guide pin and slot means associated with said base plate and with said mounting plate for guiding the movements relative to said base plate of said mounting plate and said link about said pivotal connections; and means in said mounting plate for the attachment of said distributor means for advancing or retarding said spark in response to engine operating conditions; whereby, when said base plate is attached to said distributor housing and a force is applied to said mounting plate by said means for advancing or retarding said spark, said link pivots about said pivotal connection between it and said base plate, said mounting plate pivots about said pivotal connection between it and said link, and said pivotal connection between said mounting plate and said link moves relative to said base plate, this pivotal connection movement being guided by said guide pin and slot means associated with said base plate and mounting plate.
 3. A breaker plate assembly in accordance with claim 1, wherein said mounting plate and said link are positioned on opposite sides of said base plate and wherein said guide pin and slot means comprises a slot in said mounting plate and a pin affixed to said base plate, said pin extending into said slot for movement therein.
 4. A breaker plate assembly in accordance with claim 1, wherein said mounting plate and said link are positioned on opposite sides of said base plate and wherein said pivotal connection between said link and said mounting plate comprises a pivot pin intEgral with said link and extending therefrom through said opening in said base plate to permit pivotal connection with said mounting plate, and means in contact with said pivot pin for resiliently urging said mounting plate and said link toward said base plate.
 5. A breaker plate assembly for use in an ignition distributor for a spark ignition engine, said breaker plate assembly comprising: a base plate, said base plate having an opening therein and said base plate having a recessed portion; a circuit breaker mounting plate positioned on one side of said base plate; a link positioned within said recessed portion of said base plate and on the other side thereof, said link being pivotally connected at a first point thereon to said base plate, and said link being pivotally connected at a second point thereon to said mounting plate; and guide pin and slot means associated with said mounting plate and with said base plate for guiding movements of said mounting plate and said link relative to said base plate; whereby, when said base plate is attached to said distributor and a force is applied to said mounting plate, said link pivots about said pivotal connection between it and said base plate, said mounting plate pivots about said pivotal connection between it and said link, and said pivotal connection between said mounting plate and said link moves relative to said base plate, this pivotal connection movement being guided by said guide pin and slot means associated with said mounting plate and base plate.
 6. A breaker plate assembly in accordance with claim 5, wherein said pivotal connection of said link with said base plate at said first point on said link comprises a slotted boss integral with said link and a flanged aperture in said base plate, said slotted boss being positioned within said flanged aperture.
 7. A breaker plate assembly in accordance with claim 6, wherein said pivotal connection of said link with said mounting plate at said second point on said link comprises a pivot pin integral with said link and extending through said opening in said base plate to permit pivotal connection with said mounting plate, and wherein said breaker plate assembly further comprises resilient means for urging said mounting plate and said link toward said base plate.
 8. A breaker plate assembly for use in an ignition distributor for a spark ignition engine, said breaker plate assembly comprising a base plate, said base plate having an opening therein; a circuit breaker mounting plate positioned on one side of said base plate; a link positioned on the other side of said base plate, said link being pivotally connected at a first point thereon to said base plate, said link being pivotally connected at a second point thereon to said mounting plate, said pivotal connection at said second point including a pivot pin extending through said opening in said base plate and said pivotal connection at said second point having associated therewith resilient means for urging said mounting plate and said link toward said base plate; and guide pin and slot means associated with said base plate and with said mounting plate for guiding the movements relative to said base plate of said mounting plate and said link about said first and second pivot points, said slot of said guide pin and slot means being elongated and substantially straight in shape, said guide pin of said guide pin and slot means being movable in said slot; whereby, when said base plate is attached to said distributor and a force is applied to said mounting plate, said link pivots about said pivotal connection between it and said base plate, said mounting plate pivots about said pivotal connection between it and said link, and said pivotal connection between said mounting plate and said link moves relative to said base plate, this pivotal connection movement being guided by said guide pin and slot means associated with said base plate and mounting plate. 